Field of The Invention
Automatic Swiss screw machines are metal working lathes whose automatic operation is obtained by a camshaft which controls the succession of productive operations and idle periods and the movements of all working parts. The cams may be changed or adjusted and, once set, such machines are automatic, producing a series of identical parts from a piece of bar stock.
Traditionally, these machines are limited to performing operations that require the work to be rotating, such rotation being applied by the headstock spindle within which the work is held. In order to perform operations in which the work is "stationary, such as cross drilling or the like, it has been necessary to remove the part from the screw machine and take it to another machine for the stationary operation. Alternatively, the spindle rotation must be stopped and the screw machine provided with the necessary tools to perform the stationary operation.
Stopping the spindle rotation is necessary to avoid breakage of cross milling tools and drills. Also, it is necessary in some cases to be able to properly position the operation performed by the stationary tool. Furthermore, in the case of fine tolerance parts, the rotary positioning of the work must be accomplished with accuracy so that the site of the stationary operation is precisely located.
Although newer models of these machines have means for stopping the spindles built in or available as an additional option, the mechanisms of these devices involve a complex assembly of clutches and bearings within the machines. Such assemblies require the services of an experienced mechanic to set and maintain them and are not adaptable to other types of machines or indeed to the large established base of older machines that are in current and daily use.
Recognizing the need for a simple apparatus, easily adaptable to existing automatic Swiss screw machines, the inventors herein have devised such an apparatus, comprising essentially three parts, that is simple to set up and use yet provides positive and accurate control over the rotation of the screw machine spindle.